JP6244894B2 - COMMUNICATION SYSTEM, COMMUNICATION METHOD, AND CALL CONTROL SERVER DEVICE - Google Patents

Description

  The present invention relates to a communication system, a communication method, and a call control server device.

  In the configuration of the communication carrier, a specific station is in charge of communication to a specific regional network, and the call control server executes call control corresponding to the specific station. For this reason, the call control server may be congested due to the processing load of outgoing / incoming calls with respect to a terminal located in a specific area to be managed, and therefore performs congestion control using a CPU (Central Processing Unit) usage rate.

  Specifically, the call control server monitors the CPU usage rate at a constant cycle, and if the CPU usage rate exceeds the threshold value N times (N: any natural number) continuously, it is considered as occurrence of congestion and is stepwise. Execute call control suppression.

  For example, when the average value of the CPU usage rate exceeds 75%, the call control server considers that the congestion is mild and suppresses 30% of the total call volume. Further, when the average value of the CPU usage rate exceeds 85%, the call control server regards it as severe congestion and suppresses 50% of the total call volume. Further, when the average value of the CPU usage rate exceeds 95%, the call control server considers the system congestion and suppresses 100% of the total call volume.

  The call control server rejects acceptance of a call for which it is determined to be suppressed by software control. Then, after executing the call suppression, the call control server cancels the congestion control and executes the call control for each call when the average value of the CPU usage rate falls below the threshold value.

JP 2009-296186 A JP 2010-74310 A

  However, in the above technique, the call connection is suppressed due to congestion even though there is a sufficient transmission line resource.

  For example, when a large amount of outgoing calls and incoming calls are repeatedly performed within a short period of time due to a disaster or the like, the call control server becomes congested before the accepted call is shifted to during a call or during a call. Therefore, the call control server refuses to accept the call because the CPU usage rate is high even though there is a free transmission path for establishing the call. As a result, free resources on the transmission path are wasted.

  The disclosed technology has been made in view of the above, and an object thereof is to provide a communication system, a communication method, and a call control server device that can efficiently use resources of a transmission path.

  In the first proposal, the communication system includes a first call control server device and a second call control server device. When the first call control server device detects congestion, the first call control server device transmits line information used by a terminal device that is a target of call control to the second call control server device. A transmission unit. The first call control server device includes a connection unit that receives the line information used for the call control from the second call control server device and connects to the terminal device using the received line information. The second call control server device receives a first reception unit that receives the line information from the first call control server device, and the terminal device that is transmitted to the first call control server device. And a second receiving unit for receiving the call control request. The second call control server device responds to the first call control server device with the line information received by the first reception unit when the call control request is received by the second reception unit. A response unit.

  According to one embodiment, the resources of the transmission path can be used efficiently.

FIG. 1 is a diagram illustrating an example of a carrier network according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of the communication system according to the first embodiment. FIG. 3 is a functional block diagram illustrating the functional configuration of the distribution server according to the first embodiment. FIG. 4 is a diagram illustrating an example of information stored in the call distribution table. FIG. 5 is a functional block diagram illustrating the functional configuration of the congestion call control server according to the first embodiment. FIG. 6 is a diagram illustrating an example of information stored in the station data table. FIG. 7 is a functional block diagram illustrating a functional configuration of the non-congested call control server according to the first embodiment. FIG. 8 is a diagram for explaining processing at the time of congestion according to the first embodiment. FIG. 9 is a sequence diagram illustrating the flow of processing according to the first embodiment. FIG. 10 is a flowchart showing the flow of the congestion detection process executed by the distribution server. FIG. 11 is a flowchart showing the flow of the distribution process after congestion detection executed by the distribution server. FIG. 12 is a flowchart showing a processing flow when congestion is detected in the call control server. FIG. 13 is a flowchart showing the flow of call control processing after congestion detection of the call control server. FIG. 14 is a flowchart showing the flow of call control processing of the non-congested call control server. FIG. 15 is a diagram for explaining prediction of the CPU usage rate according to the second embodiment. FIG. 16 is a diagram for explaining an example of the distribution rate based on the CPU usage rate according to the second embodiment. FIG. 17 is a diagram illustrating an example of distribution according to the second embodiment. FIG. 18 is a flowchart illustrating a flow of processing at the time of congestion prediction according to the third embodiment. FIG. 19 is a diagram for explaining congestion avoidance by pre-transmission of station data. FIG. 20 is a sequence diagram illustrating the flow of the congestion release process according to the fourth embodiment. FIG. 21 is a flowchart showing the flow of congestion release processing executed by the distribution server. FIG. 22 is a diagram illustrating a hardware configuration example.

  Hereinafter, embodiments of a communication system, a communication method, and a call control server device disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, the embodiments can be appropriately combined within a consistent range.

[overall structure]
FIG. 1 is a diagram illustrating an example of a carrier network according to the first embodiment. As shown in FIG. 1, in the carrier network 1, the region in the center 2 and the region in Hokkaido 3 are connected, and the region in the center 2 and the region in Kyushu 4 are connected. In addition, the number and kind of area shown here are examples, and are not limited to what was illustrated.

  In each region, a communication system 5 that controls SIP (Session Initiation Protocol) connection between terminals is configured. FIG. 2 is a diagram illustrating a configuration example of the communication system according to the first embodiment. As illustrated in FIG. 2, the communication system 5 includes a terminal device 6, a distribution server 10, a call control server 20, a call control server 40, a call control server 60, and a plurality of terminal devices 7.

  The terminal device 6 is a calling terminal that requests the terminal device 7 for SIP connection, and is, for example, a terminal such as a mobile phone, a smartphone, or a personal computer. The distribution server 10 is a server device that distributes the SIP connection request from the terminal device 6 to a call control server that manages the called terminal.

  The call control server 20, the call control server 40, and the call control server 60 are server devices that control voice communication and the like by establishing a path between the terminal device 6 and the terminal device 7 using SIP. The terminal device 7 is a called terminal that responds to the SIP connection from the terminal device 6, and is a terminal such as a mobile phone, a smartphone, or a personal computer.

  In such a state, in this communication system 5, the non-congested call control server performs C-PLANE control using station data of the congested call control server, and the congested call control server uses the result of the C-PLANE control. The U-PLANE control is executed to establish a path. As a result, it is possible to effectively use the resources of the transmission path.

  In this embodiment, as an example, the call control server 20 will be described as a congested call control server, and the call control server 40 and the call control server 60 will be described as non-congested call control servers.

[Device configuration]
Next, the functional configuration of each device included in the communication system 5 will be described. Since each terminal device has the same configuration as a general mobile phone, smartphone, or personal computer, detailed description is omitted. Each call control server has a function as a congestion call control server and a function as a non-congestion call control server.

(Functional configuration of distribution server)
FIG. 3 is a functional block diagram illustrating the functional configuration of the distribution server according to the first embodiment. As illustrated in FIG. 3, the distribution server 10 includes a communication control unit 11, a call distribution table 12, a usage rate monitoring unit 13, a congestion detection unit 14, a transfer instruction unit 15, a notification reception unit 16, and a distribution control unit 18. The signal transmission / reception unit 17 is provided. Each processing unit is realized by a process executed by a processor or the like or an electronic circuit included in the processor.

  The communication control unit 11 is a processing unit that controls communication of other devices, and is, for example, a network interface card. For example, the communication control unit 11 receives a SIP signal such as a SIP connection request from the terminal device 5 on the calling side, and transmits it to the corresponding call control server. Further, the communication control unit 11 receives various notifications from the call control server and the terminal device 7 on the called side.

  The call distribution table 12 is a table that stores a distribution destination at the time of congestion. The call distribution table 12 is stored in, for example, a memory or a hard disk. FIG. 4 is a diagram illustrating an example of information stored in the call distribution table.

  As shown in FIG. 4, the call distribution table 12 stores “server number, destination number, address, congestion state, distribution destination server number” in association with each other. The “server number” stored here is an identifier for identifying the call control server. “Destination number” is a destination number for which the SIP connection is requested, and here is a destination number of the terminal device 7. “Address” is the IP (Internet Protocol) address of the call control server.

  “Congestion state” is information indicating the state of the call control server. For example, “congestion” is set when congestion occurs, and “normal” is set when congestion is not occurring. The “distribution destination server number” is information indicating the server number of the call control server set as the distribution destination during congestion. The “distribution destination server number” may be set in advance by an administrator or the like, and can be set dynamically from the load status of each call control server. For example, the distribution server 10 can monitor the CPU (Central Processing Unit) load of each call control server periodically, and set the priority order from the server with the smallest load.

  In the case of FIG. 4, the IP address of the call control server 20 that controls the called number “090000” is “AAA”. Further, this call control server 20 is currently “congested”, and indicates that the call control server 40 and the call control server 60 are set as the distribution destination servers.

  The usage rate monitoring unit 13 is a processing unit that monitors the load on each call control server. Specifically, the usage rate monitoring unit 13 periodically acquires a CPU usage rate, a memory usage rate, a disk usage rate, and the like from each call control server. Then, the usage rate monitoring unit 13 outputs the acquired information to the congestion detection unit 14.

  The congestion detection unit 14 is a processing unit that detects congestion of each call control server. For example, the congestion detection unit 14 detects a call control server in which the average of N times of CPU usage rates acquired by the usage rate monitoring unit 13 exceeds a threshold as a call control server in which congestion occurs. When congestion is detected, the congestion detection unit 14 updates the congestion state of the call distribution table 12 to “congestion”.

  As another example, the congestion detection unit 14 detects a call control server that has exceeded a threshold value for N consecutive times of CPU usage as a call control server in which congestion has occurred. Then, the congestion detection unit 14 specifies the server number of the call control server in which congestion is detected from the call distribution table 12 and outputs it to the transfer instruction unit 15.

  The transfer instruction unit 15 is a processing unit that instructs the call control server in which congestion is detected to transfer station data. For example, when “server number = 20” is notified from the congestion detection unit 14, the transfer instruction unit 15 specifies the IP address “AAA” of the corresponding call control server 20 from the call distribution table 12. Then, the transfer instruction unit 15 transmits an instruction to transfer station data to the IP address “AAA”.

  Further, the transfer instruction unit 15 specifies “distribution destination server numbers = 40, 60” corresponding to “server number = 20” notified from the congestion detection unit 14. Then, the transfer instruction unit 15 specifies the IP address “BBB” corresponding to “allocation destination server number = 40” and the IP address “CCC” corresponding to “allocation destination server number = 60”. Thereafter, the transfer instruction unit 15 can also transmit the IP addresses “BBB” and “CCC” of the distribution destination together with the transfer instruction of the station data.

  The notification receiving unit 16 is a processing unit that receives various notifications from each call control server. For example, the notification receiving unit 16 receives, via the communication control unit 11, a completion notification for a station data transfer instruction and a completion notification for a transferred station data deletion instruction.

  The signal transmission / reception unit 17 is a processing unit that receives a SIP signal such as a SIP connection request from the terminal device 6. For example, the signal transmission / reception unit 17 receives a SIP INVITE signal from the terminal device 6 and outputs the SIP INVITE signal to the distribution control unit 18.

  The distribution control unit 18 is a processing unit that distributes the SIP signal to the corresponding call control server. Specifically, the distribution control unit 18 refers to the call distribution table 12, identifies the corresponding call control server, and transmits a SIP signal to the identified call control server.

  For example, the distribution control unit 18 extracts the destination number “090000” from the SIP INVITE signal. Then, the distribution control unit 18 specifies the server number “20” and the address “AAA” associated with the called number “090000” from the call distribution table 12.

  Here, when the congestion state associated with the combination of the server number “20” and the address “AAA” is “normal”, the distribution control unit 18 transmits a SIP INVITE signal to the address “AAA”. To do.

  On the other hand, when the congestion state associated with the combination of the server number “20” and the address “AAA” is “congestion”, the distribution control unit 18 determines the distribution destination server number “40” associated with the combination. And “60”. Then, the distribution control unit 18 specifies one of the distribution destination server numbers “40” and “60”, and transmits a SIP INVITE signal to the specified address.

  The distribution control unit 18 can determine an arbitrary server among the distribution destination server numbers “40” and “60” as the distribution destination. In addition, the distribution control unit 18 may determine a distribution destination server number “40” or “60” having a lower CPU usage rate as a distribution destination, or simply perform distribution alternately.

(Functional configuration of congestion call control server)
FIG. 5 is a functional block diagram illustrating the functional configuration of the congestion call control server according to the first embodiment. As shown in FIG. 5, the congestion call control server 20 includes a software control device 21 and a U-PLANE control device 25. The software control device 21 and the U-PLANE control device 25 are realized by a process executed by a processor or the like or an electronic circuit included in the processor.

  The software control device 21 includes a signal distribution control unit 22, a C-PLANE control unit 23, and a U-PLANE control unit 24, and performs a C-PLANE control and a U-PLANE control on the SIP signal by these. Part.

  The signal distribution control unit 22 is a processing unit that executes distribution to a control unit corresponding to each call. Specifically, the signal distribution control unit 22 determines the type of the received SIP signal and various notifications, and distributes it to the control unit that executes the signal and the like.

  For example, the signal distribution control unit 22 outputs the station data transfer instruction or the like from the distribution server 10 to the congestion detection unit 23b. Moreover, the signal distribution control part 22 is output to the incoming signal control part 23d, when a SIP signal, C-PLANE information, etc. are received from the distribution server 10. FIG.

  The C-PLANE control unit 23 is a processing unit that executes various processes related to C-PLANE that performs protocol stacking and control. The C-PLANE control unit 23 includes a station data table 23a, a congestion detection unit 23b, a station data transmission unit 23c, an incoming signal control unit 23d, a signal analysis unit 23e, a session control unit 23f, and a service control unit 23g. The C-PLANE control unit 23 can also generate an incoming signal control unit 23d, a signal analysis unit 23e, a session control unit 23f, and a service control unit 23g by call-by-call.

  The station data table 23 a is a table that stores station data indicating information of terminal devices located in a specific area managed by the congestion call control server 20. The station data table 23a is stored in, for example, a memory or a hard disk. FIG. 6 is a diagram illustrating an example of information stored in the station data table. As illustrated in FIG. 6, the station data table 23 a stores “calling number, line, ground, transmission destination” in association with each other.

  The “calling number” stored here is a telephone number that identifies the terminal device 7 on the called side. “Line” is information indicating the type of line used by the terminal device 7, and is set to “STM” for an STM (Synchronous Transfer Mode) line, and “ATM” for an ATM (Asynchronous Transfer Mode) line. Is set. “Ground” is information indicating an area where the terminal device 7 is installed. “Destination” is the IP address of the terminal device 7.

  In the case of FIG. 6, the terminal device 7 having the incoming call number “090111” and the transmission destination address A installed in the region 1 indicates that the path connection is performed using the STM.

  The congestion detection unit 23b is a processing unit that detects congestion. Specifically, when the congestion detection unit 23b periodically transmits a load status such as a CPU usage rate to the distribution server 10 and receives a notification indicating a congestion state from the distribution server 10, the call control server 23b Is detected as being congested.

  Then, the congestion detector 23b notifies the station data transmitter 23c that congestion has been detected. When the congestion detection unit 23b receives the allocation destination together with the congestion detection notification, the congestion detection unit 23b also notifies the station data transmission unit 23c of the allocation destination. The congestion detection unit 23b can also detect congestion by itself using the same method as the distribution server 10.

  The station data transmission unit 23c is a processing unit that transmits station data to another call control server. Specifically, the station data transmission unit 23c, when congestion is detected by the congestion detection unit 23b and a transmission instruction is received from the distribution server 10, the station data stored in the station data table 23a is transferred to another call control server. Send to.

  For example, the station data transmission unit 23c transmits the station data to the call control server designated by the distribution server 10. The station data transmission unit 23c can also transmit the station data to a call control server preset as a distribution destination by the administrator or a call control server nearest to the network. In this case, the station data transmission unit 23c transmits the address of the call control server that is the destination of the station data to the distribution server 10 together with the notification that the transmission of the station data has been completed.

  The incoming signal control unit 23d is a processing unit that executes protocol control. Specifically, when receiving the SIP signal or C-PLANE information received from the distribution server 10, the incoming signal control unit 23d executes reception processing, transmits a reception response, and outputs a signal to the corresponding processing unit. Execute. For example, the ingress signal controller 23d outputs the received SIP signal and C-PLANE information to the signal analyzer 23e.

  The signal analysis unit 23e is a processing unit that analyzes the received signal and executes processing according to the analysis result. For example, when a SIP INVITE signal is input from the incoming signal control unit 23d, the signal analysis unit 23e extracts the incoming call number “090111” from the INVITE signal. Then, the signal analysis unit 23e refers to the station data table 23a and specifies that the transmission destination corresponding to “090111” is “transmission destination address A” and the line to be used is “STM”. Thereafter, the signal analysis unit 23e outputs the identified transmission destination and line information to the session control unit 23f.

  In addition, when the C-PLANE information is input from the incoming signal control unit 23d, the signal analysis unit 23e has the transmission destination “destination address A” and the line to be used is “STM” from the C-PLANE information. Identify that there is. Thereafter, the signal analysis unit 23e outputs the identified transmission destination and line information to the session control unit 23f.

  The session control unit 23f is a processing unit that distributes a received signal to a service control unit that performs a service on the received signal. For example, when the session control unit 23f receives the transmission destination “transmission destination address A” and the used line “STM” from the signal analysis unit 23e, the session control unit 23f sends the transmission destination “transmission” to the service control unit that executes the service using the STM line. The destination address A "and the used line" STM "are output.

  The service control unit 23g is a processing unit that executes a service corresponding to the received signal. The service control unit 23g may be provided for each service. For example, when the transmission destination “transmission destination address A” and the used line “STM” are input from the session control unit 23f, the service control unit 23g establishes a path with “transmission destination address A” using “STM”. The instruction is output to the U-PLANE control unit 24.

  The U-PLANE control unit 24 is a processing unit that executes various processes related to U-PALNE that handles user data. The U-PLANE control unit 24 includes an outgoing signal control unit 24a, an STM line control unit 24b, and an ATM line control unit 24c.

  The outgoing signal control unit 24a is a processing unit that instructs a path connection to the control unit corresponding to the requested line type, and when a U-PLANE path is established, an ISUP (Integrated Services Digital Network User Part). A processing unit that transmits a signal to the called side.

  For example, when the outgoing signal control unit 24a receives an instruction to establish a path with "destination address A" using "STM" from the service control unit 23g, the outgoing signal control unit 24a establishes a path using STM to the STM line control unit 24b. Request. When the STM path is established, the outgoing-side signal control unit 24a performs an ISUP_IAM (Initial Address Message) including the caller telephone number and the called party telephone number with respect to the “destination address A” on the called side. Signals and BISUP_IAM signals are transmitted via the signal distribution control unit 22.

  When the outgoing signal control unit 24a receives an instruction to establish a path with "destination address B" using "ATM" from the service control unit 23g, the outgoing signal control unit 24a establishes a path establishment using ATM to the ATM line control unit 24c. Request. When the ATM path is established, the outgoing signal control unit 24a transmits the ISUP_IAM signal and the BISUP_IAM signal to the destination transmission destination address B via the signal distribution control unit 22. To do.

  The STM line control unit 24b is a processing unit that connects the path between the calling side and the called side through an STM line. For example, when the STM line control unit 24b receives an instruction to establish a path with “destination address A” using “STM”, the STM line control unit 24b transmits and receives a voice signal using the STM physical line of the U-PLANE control device 25. A path to be established is established between the calling side and the called side.

  The ATM line control unit 24c is a processing unit that connects paths between the calling side and the called side through an ATM line. For example, when the ATM line control unit 24c receives an instruction to establish a path with “destination address B” using “ATM”, the ATM line control unit 24c transmits and receives a voice signal using the ATM physical line of the U-PLANE control device 25. A path to be established is established between the calling side and the called side.

  The U-PLANE control device 25 is a processing unit that establishes a U-PLANE path. This U-PLANE control device 25 has physical lines such as STM physical line 25a-1 to STM physical line 25a-n, ATM physical line 25b-1 to ATM physical line 25b-n (n: natural number). Using this physical line, the U-PLANE control unit 24 of the software control device 21 executes path connection.

(Functional configuration of non-congested call control server)
FIG. 7 is a functional block diagram illustrating a functional configuration of the non-congested call control server according to the first embodiment. As shown in FIG. 7, the non-congested call control server 40 includes a software control device 41 and a U-PLANE control device 45 having the same functions as the congestion call control server 20. Note that the software control device 41 and the U-PLANE control device 45 are realized by a process executed by a processor or the like and an electronic circuit included in the processor.

  7, the local station data table 43a, the other station data table 43b, the station data receiver 43c, and the signal analyzer 43e of the C-PLANE control 43 having functions different from those in FIG. 5 will be described.

  The ingress signal controller 43d, the session controller 43f, and the service controller 43g have the same functions as the ingress signal controller 23d, the session controller 23f, and the service controller 23g described in FIG. The U-PLANE control unit 44 has the same function as the U-PLANE control unit 24 described in FIG. 5, and the U-PLANE control unit 45 is the same as the U-PLANE control unit 25 described in FIG. It has the function of.

  The own station data table 43 a is a table that stores station data indicating information of terminal devices located in a specific area managed by the non-congested call control server 40. The own station data table 43a is stored in, for example, a memory or a hard disk. The stored information is the same as in FIG. 6, and detailed description thereof is omitted.

  The other station data table 43 b is station data received from the congestion call control server 20 and stores station data indicating information of terminal devices located in a specific area managed by the congestion call control server 20. The other station data table 43b is stored in, for example, a memory or a hard disk. The stored information is the same as in FIG. 6, and detailed description thereof is omitted.

  The station data receiving unit 43 c is a processing unit that receives station data from the congestion call control server 20. For example, the station data receiving unit 43c receives station data from the congestion call control server 20 in which congestion is detected, and stores it in the other station data table 43b.

  Further, the station data receiving unit 43c may store information specifying the transmission source congestion call control server 20 in association with the station data stored in the other station data table 43b. By doing so, even if a plurality of congestion call control servers are generated, it is possible to determine which congestion call control server station data is.

  The signal analysis unit 43e is a processing unit that analyzes the received signal and executes processing according to the analysis result. For example, the signal analysis unit 43e extracts the incoming call number from the received INVITE signal. And the signal analysis part 43e performs the process similar to the signal analysis part 23e demonstrated in FIG. 5, when the transmission destination corresponding to the extracted incoming call number is memorize | stored in the local station data table 43a.

  On the other hand, when the incoming call number extracted from the received INVITE signal is stored in the other station data table 43b instead of the own station data table 43a, the signal analysis unit 43e performs notification to the congestion call control server 20 To do. For example, the signal analysis unit 43e specifies a transmission destination and a line corresponding to the incoming call number from the other station data table 43b, and transmits the specified transmission destination and the line to the congestion call control server 20 as C-PLANE information. At this time, the signal analysis unit 43e adds the identifier of the call control server that is the transmission source of the station data to the incoming call number in the other station data table 43b, so that the congestion that becomes the transmission destination of the C-PLANE information is obtained. The call control server 20 can be specified.

[Description of processing]
FIG. 8 is a diagram for explaining processing at the time of congestion according to the first embodiment. As shown in FIG. 8, when the call control server 20 becomes congested (S1), the distribution server 10 detects the call control server 20 congestion (S2).

  Subsequently, the distribution server 10 detects congestion and instructs the call control server 20 to transfer station data (S3). Receiving this instruction, the call control server 20 transmits the station data to the call control server 40 (S4).

  Thereafter, a SIP connection request is transmitted from the terminal device 6 to the terminal device 7 (S5). The distribution server 10 transmits to the call control server 40 instead of the call control server 20 connected to the terminal device 7 (S6).

  The call control server 40 executes C-PLANE control according to the SIP connection request, and transmits C-PLAN information to the call control server 20 (S7).

  Then, the call control server 20 identifies the line and the called side based on the C-PLANE control received from the call control server 40, and connects the terminal device 6 on the calling side and the terminal device 7 on the called side with a path ( S8 and S9).

[Process flow]
Next, the flow of processing executed by the communication system 5 will be described. Here, the overall flow, the distribution server process, the congestion call control server process, and the non-congestion call control server process will be described.

(Overall processing flow)
FIG. 9 is a sequence diagram illustrating the flow of processing according to the first embodiment. As shown in FIG. 9, the distribution server 10 transmits a CPU usage rate acquisition request to the call control server 20 and the call control server 40 (S101 to S103).

  The call control server 20 receives the CPU usage rate acquisition request, acquires the CPU usage rate, and responds to the distribution server 10 (S104 and S105). Similarly, the call control server 40 receives the CPU usage rate acquisition request, acquires the CPU usage rate, and responds to the distribution server 10 (S106 and S107).

  Thereafter, the distribution server 10 detects congestion of the call control server 20 from the acquired CPU usage rate of each call control server (S108), and instructs the call control server 20 to transmit station data (S109 and S110). .

  The call control server 20 receives the station data transmission instruction from the distribution server 10 (S111), reads the station data from the station data table 23a, and transmits it to the call control server 40 which is not congested (S112 and S113).

  Subsequently, when the call control server 40 receives the station data from the congested call control server 20 and holds it in a memory or the like (S114), the call control server 40 transmits a reception notification to the call control server 20 (S115 and S116).

  The call control server 20 that has received the reception notification transmits a station data transmission completion notification to the distribution server 10 (S117 and S118). Upon receiving the station data transmission completion notification, the distribution server 10 updates the congestion state and the distribution destination server number in the call distribution table 12 (S119).

  After that, when receiving the SIP INVITE signal from the originating terminal device 6 (S120), the distribution server 10 transmits the received SIP INVITE signal to the call control server 40 of the distribution destination (S121 and S122). . Specifically, the distribution server 10 specifies a call control server that manages the called number based on the called number included in the INVITE signal and the call distribution table 12. At this time, when the call control server is congested, the distribution server 10 transmits an INVITE signal to the distribution destination.

  The call control server 40 receives the SIP INVITE signal to be processed by the call control server 20 from the distribution server 10 (S123), and specifies the signal information and the line information on behalf of the congested call control server 20. Then, the call control server 20 is notified (S124 and S125). Specifically, the call control server 40 refers to the other station data table 43b using the called number included in the INVITE signal as a key, identifies and notifies the transmission destination and the line.

  Thereafter, the call control server 20 identifies a physical resource based on the received signal information and line information (S126), and connects a path between the terminal device 7 on the called side and the terminal device 6 on the calling side (S127). Further, the call control server 20 transmits information such as ISUP to the called terminal device 7 (S128 and S129). Specifically, the call control server 20 connects the notified transmission destination and the transmission source using the notified line.

(Flow of distribution server congestion detection processing)
FIG. 10 is a flowchart showing the flow of the congestion detection process executed by the distribution server. This process is executed for each call control server. Here, the call control server 20 will be described as an example.

  As illustrated in FIG. 10, when the usage rate monitoring unit 13 of the distribution server 10 reaches a cycle T that is a monitoring cycle (S201: Yes), the usage rate monitoring unit 13 acquires a CPU usage rate from the call control server 20 (S202).

  Subsequently, the congestion detection unit 14 determines whether the notification is the Nth CPU usage rate notification (S203). If the CPU usage rate notification is less than the Nth time (S203: No), the CPU usage rate is integrated. The number of notifications is incremented (S204). On the other hand, when there are N notifications (S203: Yes), the congestion detection unit 14 integrates the CPU usage rate and calculates an average value of N times (S205).

  After that, when the average value of the CPU usage rate is smaller than the threshold (S206: No), the congestion detection unit 14 initializes the CPU usage rate and initializes the number of notifications (S207). That is, the congestion detection unit 14 sets the CPU usage rate and the number of notifications to 0.

  On the other hand, when the average value of the CPU usage rate is larger than the threshold value (S206: Yes), the transfer instruction unit 15 notifies the call control server 20 of the occurrence of congestion (S208). Subsequently, the transfer instruction unit 15 instructs the call control server 20 to transmit station data (S209). At this time, the transfer instruction unit 15 may notify the transmission destination of the station data.

(Distribution server flow)
FIG. 11 is a flowchart showing the flow of the distribution process after congestion detection executed by the distribution server. This process is executed for the congestion call control server. Here, the call control server 20 will be described as an example of the congestion call control server 20.

  As shown in FIG. 11, the notification receiving unit 16 of the distribution server 10 receives a notification of the completion of station data transmission from the congestion call control server 20 (S301). Then, the notification receiving unit 16 updates the call distribution table 12 when the distribution destination or the like is described in the received completion notification (S302).

  After that, when receiving the SIP signal (S303: Yes), the signal transmitting / receiving unit 17 refers to the call distribution table 12 to specify the distribution destination (S304) and receives it at the call control server of the specified distribution destination. The SIP signal thus transmitted is transmitted (S305).

(Flow of processing when congestion is detected in the call control server)
FIG. 12 is a flowchart showing a processing flow when congestion is detected in the call control server. Here, the call control server 20 will be described as an example.

  As shown in FIG. 12, when a signal is received (S401: Yes), the signal distribution control unit 22 of the call control server 20 determines the distribution server 10 from the header of the signal, the identification or message included in the signal, and the like. It is determined whether or not it is a congestion notification transmitted (S402).

  If the received signal is not a congestion notification (S402; No), the session control unit 23f and the service control unit 23g execute processing corresponding to the signal (S403). In other words. The call control server 20 executes general C-PLANE control and U-PLANE control.

  On the other hand, when the signal distribution control unit 22 determines that it is a congestion notification (S402: Yes), the congestion detection unit 23b and the like specify a route that is congested from the traffic (S404).

  Thereafter, when an instruction to transmit station data is received (S405: Yes), the station data transmitting unit 23c reads the station data from the station data table 23a and transmits it to the non-congested call control server (S406).

  When the station data transmission unit 23c receives the reception notification of the station data from the non-congested call control server (S407: Yes), the station data transmission unit 23c notifies the distribution server 10 of the completion of the transmission of the station data (S408).

(Flow of call control processing after congestion detection of the call control server)
FIG. 13 is a flowchart showing the flow of call control processing after congestion detection of the call control server. Here, the call control server 20 will be described as an example.

  As shown in FIG. 13, when a signal is received (S501: Yes), the signal distribution control unit 22 of the call control server 20 determines the non-congested call control from the header of the signal, the identification or message included in the signal, and the like. It is determined whether or not the C-PLANE information is transmitted by the server (S502).

  When the received signal is not C-PLANE information (S502; No), the session control unit 23f and the service control unit 23g execute processing according to the signal (S503).

  On the other hand, when the signal distribution control unit 22 determines that the information is C-PLANE information (S502: Yes), the signal analysis unit 23e extracts line information from the received signal (S504). At this time, the signal analysis unit 23e also extracts the incoming call number from the received signal and identifies the terminal device 7 on the called side.

  Subsequently, the session control unit 23f identifies the used line from the line information and captures the U-PLANE resource (S505). If the line information is STM (S506: Yes), the U-PLANE control unit 24 refers to the U-PLANE control device 25 to search for an STM free line (S507).

  Then, the U-PLANE control unit 24 requests the U-PLANE control device 25 to establish a path connection using an available STM line, and the U-PLANE control device 25 uses the available STM line to make a caller side and a destination side. Are connected (S508). Thereafter, when the path is connected, the outgoing signal control unit 24a transmits an ISUP signal to the called side (S509).

  On the other hand, when the line information is not STM (S506: No), the U-PLANE control unit 24 refers to the U-PLANE control device 25 to search for an ATM free line (S510).

  Then, when the line information is ATM (S510: Yes), the U-PLANE control unit 24 executes S511. That is, the U-PLANE control unit 24 requests the U-PLANE control device 25 to establish a path connection using an available ATM line, and the U-PLANE control device 25 uses the available ATM line to send and receive calls. And connect the path. Thereafter, when the path is connected, the outgoing signal control unit 24a transmits an ISUP signal to the called side (S509).

  When the line information is not ATM (S510: No), the session control unit 23f disconnects the call (S512).

(Flow of call control processing of non-congested call control server)
FIG. 14 is a flowchart showing the flow of call control processing of the non-congested call control server. Here, the call control server 40 will be described as an example.

  As shown in FIG. 14, when the signal distribution control unit 42 of the call control server 40, which is a non-congested server, receives a signal (S601: Yes), the received signal is a congestion call based on the identification or message included in the signal. It is determined whether the station data is transmitted by the control server (S602).

  If the received signal is station data of another station (S602: Yes), the station data receiving unit 43c stores the received station data of the other station in the other station data table 43b (S603). At this time, the station data receiving unit 43c may store an identifier for identifying the call control server of the transmission source in association with each other.

  On the other hand, when the received signal is not a station data of another station but a normal SIP signal (S602: No), the incoming signal control unit 43d executes protocol control including reception processing such as a reception response (S604). .

  Subsequently, the signal analysis unit 43e searches the local station data table 43a using the incoming call number included in the received SIP signal as a key (S605). When the incoming call number is stored in the own station data table 43a (S606: Yes), the session control unit 43f and the service control unit 43g execute service control including identification of the used line and identification of the called side. (S607).

  On the other hand, when the incoming call number is not stored in the own station data table 43a (S606: No) and is stored in the other station data table 43b (S608: Yes), the signal analysis unit 43e executes S609. . That is, the signal analysis unit 43e adds a transfer identifier for identifying that the data is a transfer target to the received other station data. As a result, a transfer identifier is added to the processing result using the received other station data. Thereafter, the session control unit 43f and the service control unit 43g execute S607.

  When the received data is not other station data (S608: No), the session control unit 43f disconnects the call (S610).

  After that, when the transfer identifier is not added (S611: No), the session control unit 43f and the service control unit 43g transmit U-PLANE control including path connection using the transmission path resource of the local station and transmission of the ISUP signal. C-PLANE control including the above is executed (S612).

  On the other hand, when the transfer identifier is added (S611: Yes), the signal analysis unit 43e transmits C-PLANE information including the transmission destination and line information to the congestion call control server 20 (S613).

[effect]
As described above, in the communication system 5, even when the call traffic to the call control server suddenly increases and the CPU load increases, the call control server that is not congested can perform the C-PLANE control. Therefore, the congested call control server can execute the path connection only by executing the U-PLANE which can be executed even when the CPU load is small and the congestion is present. As a result, the transmission path resources of the congested call control server can be effectively used. In addition, since the transmission path resource of the call control server can be effectively used, the connection rate of the telephone service can be increased.

  By the way, in the first embodiment, the example in which the call connection of the congestion call control server is distributed to one non-congestion call control server has been described, but the present invention is not limited to this. For example, the transition of the CPU usage rate of each non-congested call control server can be predicted, and the distribution rate to each non-congested call control server can be determined from the predicted CPU usage rate.

  Therefore, in the second embodiment, an example will be described in which the distribution rate to each non-congested call control server is determined from the prediction result of the CPU usage rate and the load is distributed. FIG. 15 is a diagram for explaining prediction of the CPU usage rate according to the second embodiment. As illustrated in FIG. 15, the distribution server 10 calculates a differential coefficient of a change in the CPU usage rate between the current time and the past time, and predicts a transition of the CPU usage rate from the differential coefficient.

  For example, the prediction of the CPU usage rate at the future time t4 when the current time is t3 will be described. The distribution server 10 can calculate from “CPU usage rate at future time t4 = CPU usage rate at current time t3 + (ΔCPU usage rate / Δt) × (future time t4−current time t3)”. The ΔCPU usage rate can be calculated by “CPU usage rate at current time t3−CPU usage rate at past time t2”, and Δt can be calculated as “current time t3—past time t2”.

  For example, if the allocation server 10 predicts that the CPU usage rate at the future time t4 of the call control server 40 that is not congested is 10% and the CPU usage rate at the future time t4 of the call control server 60 is 20%, The rate is determined as “call control server 40: call control server 60 = 1: 2.”

  FIG. 16 is a diagram for explaining an example of the distribution rate based on the CPU usage rate according to the second embodiment. FIG. 16 shows the structure of the call distribution table. As shown in FIG. 16, the call distribution table 12 of the distribution server 10 holds “call distribution ratio” in addition to the information described in FIG. 4 of the first embodiment. The “call distribution rate” is a rate of distributing calls from the congestion call control server, and is determined from the CPU usage rate prediction result. In the case of FIG. 16, it shows that the call of the call control server 20 in congestion is distributed to the call control server 40 and the call control server 60 by 1: 2.

  This will be specifically described with reference to FIG. FIG. 17 is a diagram illustrating an example of distribution according to the second embodiment. The system diagram shown in FIG. 17 illustrates an example in which the call control server 20 is in a congested state, and the call of the call control server 20 that is congested is distributed 1: 2 between the call control server 40 and the call control server 60. ing.

  As shown in FIG. 17, when the distribution server 10 receives the three signals of the SIP signal A, the SIP signal B, and the SIP signal C in order, the distribution ratio is 1: 2, so that one signal is received. It transmits to the call control server 40 and transmits two SIP signals to the call control server 60. For example, the distribution server 10 transmits the SIP signal A to the call control server 40 and transmits the SIP signal B and the SIP signal C to the call control server 60.

  As described above, in the second embodiment, the distribution server 10 dynamically changes the distribution ratio according to the CPU usage rate of the distribution destination, and distributes and processes the call of the congested call control server. Can do. That is, the distribution server 10 can perform distribution so as to smooth the CPU. For this reason, it can suppress that the call of the congested call control server concentrates on one non-congested call control server. Therefore, since the processing load of the non-congested call control server can be reduced, it is possible to suppress the non-congested call control server from being congested by processing the call of the congested call control server.

  In the first embodiment, the example in which the station data is transmitted when congestion is detected has been described. However, the present invention is not limited to this. For example, the station data can be transmitted in advance before the congestion. Therefore, in the third embodiment, an example in which occurrence of congestion is predicted and station data is transmitted before the congestion will be described.

  Here, an example in which a load transition of the CPU usage rate is predicted will be described, but the same method as in the second embodiment can be used as the prediction method. FIG. 18 is a flowchart illustrating the flow of processing at the time of congestion prediction according to the third embodiment. This process is executed for each call control server. Here, the call control server 20 will be described as an example.

  As illustrated in FIG. 18, when the usage rate monitoring unit 13 of the distribution server 10 reaches a cycle T that is a monitoring cycle (S701: Yes), the CPU usage rate is acquired from the call control server 20 (S702).

  Subsequently, the congestion detection unit 14 determines whether the notification is the Nth CPU usage rate notification (S703). When the CPU usage rate notification is less than the Nth time (S703: No), the CPU usage rate is integrated. The notification count is incremented (S704). On the other hand, when the notification is the Nth notification (S703: Yes), the congestion detection unit 14 integrates the CPU usage rate and calculates an average value of N times (S704).

  Thereafter, when the average value of the CPU usage rate is larger than the threshold (S706: Yes), the transfer instruction unit 15 notifies the call control server 20 of the occurrence of congestion (S707). Subsequently, the transfer instruction unit 15 instructs the call control server 20 to transmit station data (S708).

  On the other hand, when the average value of the CPU usage rate is smaller than the threshold (S706: No), the congestion detection unit 14 predicts the CPU usage rate after T seconds (S708). When the predicted value exceeds the threshold (S709: Yes), the congestion detection unit 14 notifies the call control server 20 of the occurrence of congestion (S707). Subsequently, the transfer instruction unit 15 instructs the call control server 20 to transmit station data (S710).

  On the other hand, when the predicted value does not exceed the threshold (S709: No), the congestion detection unit 14 adds up the CPU usage rate and increments the notification count (S704).

  FIG. 19 is a diagram for explaining congestion avoidance by pre-transmission of station data. A graph X shown in FIG. 19 shows a change in CPU usage rate when the congestion prediction is used, and a graph Y shown in FIG. 20 shows a change in CPU usage rate when the congestion prediction is not used.

  In the graph Y of FIG. 19, when the CPU usage rate is increasing, the CPU usage rate is increased by the transmission processing of the station data by transmitting the station data to the other call control server after the congestion. May fail.

  On the other hand, since the graph X in FIG. 19 executes the transfer of the station data before the congestion, the increase in the CPU usage rate due to the transmission of the station data can be suppressed. For this reason, the risk of system down due to a rapid increase in the CPU usage rate can be reduced.

  In the fourth embodiment, processing after congestion release will be described. FIG. 20 is a sequence diagram illustrating the flow of the congestion release process according to the fourth embodiment. In this embodiment, the call control server 20 is in a congestion state, and the call control server 40 is in a non-congestion state.

(Processing sequence)
As shown in FIG. 20, the distribution server 10 transmits a CPU usage rate acquisition request to the call control server 20 and the call control server 40 (S801 to S803). The call control server 20 receives the CPU usage rate acquisition request, acquires the CPU usage rate, and responds to the distribution server 10 (S804 and S805). Similarly, the call control server 40 receives the CPU usage rate acquisition request, acquires the CPU usage rate, and responds to the distribution server 10 (S806 and S807).

  Thereafter, the distribution server 10 detects the congestion release of the call control server 20 from the acquired CPU usage rate of each call control server (S808), and transmits a congestion release notification to the call control server 20 (S809 and S810). ).

  When the call control server 20 receives the notification of congestion release from the distribution server 10 (S811), the call control server 20 transmits a request to delete the transmitted station data to the call control server 40 that transmitted the station data (S812 and S813). .

  Subsequently, the call control server 40 deletes the station data received from the congested call control server 20 in a memory or the like (S814), and transmits a deletion notification to the call control server 20 (S815 and S816).

  Receiving this deletion notification, the call control server 20 transmits a station data deletion completion notification to the distribution server 10 (S817 and S818). Upon receiving the station data deletion completion notification, the distribution server 10 updates the congestion state and the distribution destination server number in the call distribution table 12 (S819).

  After that, when receiving the SIP INVITE signal from the originating terminal device 6 (S820), the distribution server 10 transmits the received SIP INVITE signal to the call control server 20 (S821 and S822).

  Thereafter, the call control server 20 specifies signal information and line information based on the received INVITE signal, and specifies a physical resource used for the path (S824). Further, the call control server 20 connects a path between the terminal device 7 on the called side and the terminal device 6 on the calling side (S825). Further, the call control server 20 transmits information such as ISUP to the terminal device 7 on the called side (S826 and S827).

(flowchart)
FIG. 21 is a flowchart showing the flow of congestion release processing executed by the distribution server. This process is executed for each call control server. Here, the call control server 20 will be described as an example.

  As shown in FIG. 21, when the usage rate monitoring unit 13 of the distribution server 10 reaches the cycle T that is the monitoring cycle (S901: Yes), the CPU usage rate is acquired from the call control server 20 (S902).

  Subsequently, the congestion detection unit 14 determines whether the notification is the Nth CPU usage rate notification (S903). If the CPU usage rate notification is less than the Nth time (S903: No), the CPU usage rate is integrated. The number of notifications is incremented (S904).

  On the other hand, when the notification is the Nth notification (S903: Yes), the congestion detection unit 14 refers to the call distribution table 12 and determines whether or not the target call control server 20 is in a congestion state (S905). At this time, when the target call control server 20 is not in a congestion state (S905: No), the congestion detection unit 14 executes the congestion detection process shown in FIG. 10 (S906).

  Then, when the target call control server 20 is in a congested state (S905: Yes), the congestion detection unit 14 integrates the CPU usage rate and calculates an average value of N times (S907). After that, when the average value of the CPU usage rate is larger than the threshold (S908: No), the congestion detection unit 14 initializes the CPU usage rate and initializes the number of notifications (S909).

  On the other hand, when the average value of the CPU usage rate is smaller than the threshold (S908: Yes), the congestion detection unit 14 determines whether the release time has been set (S910). Here, the release time is a time during which a fixed time after the congestion is released is not released. That is, control is performed so that the original state is restored after the cancellation time elapses after the congestion is detected. By doing so, it is possible to prevent the congestion of the call control server from being induced by returning to the original state immediately after the congestion is released and causing the congested call control server to execute the C-PLANE control.

  If the release time has not been set (S910: No), the congestion detection unit 14 sets the release time (S911), sets a pre-designated call distribution rate (S912), and executes S909. . Here, the call distribution rate is a distribution rate between the congestion call control server and the non-congestion call control server until the release time elapses.

  On the other hand, when the release time has already been set (S910: Yes) and the release time has been exceeded (S913: Yes), the congestion detection unit 14 initializes the number of notifications (S914), and the congestion detection unit 14 cancels the congestion. (S915). If the release time has already been set (S910: Yes), but the release time has not been exceeded (S913: No), the congestion detection unit 14 executes S909.

(effect)
As described above, when the congestion is released, the communication system 5 automatically recovers to the state before the congestion is released, so that the workload of the administrator can be reduced. In addition, since the other station data held by the non-congested call control server is automatically deleted, it is possible to suppress a decrease in security. In addition, by providing the congestion release time, the induction of congestion can be suppressed and the reliability can be improved.

  Although the embodiments of the present invention have been described so far, the present invention may be implemented in various different forms other than the embodiments described above. Therefore, different embodiments will be described below.

(Gradual congestion release)
For example, when the congestion of the congested call control server is released, the distribution server 10 can also suppress the recurrence of the congestion firmly by releasing it in stages. Specifically, the distribution server 10 controls the threshold value of the CPU usage rate step by step.

  For example, when the CPU usage rate of the congestion call control server falls below the threshold defined as the first stage, the distribution server 10 performs the call distribution between the non-congestion call control server and the congestion call control server in 2: 1. . Subsequently, when the CPU usage rate of the congestion call control server falls below the threshold defined as the second stage, the distribution server 10 performs the call distribution between the non-congestion call control server and the congestion call control server by 1: 1. Do.

  Furthermore, when the CPU usage rate of the congestion call control server falls below the threshold defined as the third stage, the distribution server 10 considers that the congestion is completely canceled and does not distribute to the non-congested call control server. All calls are distributed to the released call control server. By doing in this way, it can suppress that the processing load of the call control server from which congestion was canceled increases rapidly. In addition, the threshold value of each stage, the number of stages, and the distribution ratio are examples, and can be arbitrarily changed.

(system)
In addition, among the processes described in the present embodiment, all or a part of the processes described as being automatically performed can be manually performed. Alternatively, all or part of the processing described as being performed manually can be automatically performed by a known method. In addition, the processing procedure, control procedure, specific name, and information including various data and parameters shown in the above-described document and drawings can be arbitrarily changed unless otherwise specified.

  Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution and integration of each device is not limited to the illustrated one. That is, all or a part of them can be configured to be functionally or physically distributed / integrated in arbitrary units according to various loads or usage conditions. Further, all or any part of each processing function performed in each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

(hardware)
Next, a hardware configuration example of each server will be described. Since each server has the same hardware configuration, the server 100 will be described here.

  FIG. 22 is a diagram illustrating a hardware configuration example. As illustrated in FIG. 22, the server 100 includes a CPU 101, a memory 102, a communication interface 103, and an HDD (Hard Disk Drive) 104. Each unit shown in FIG. 22 is connected to each other by a bus or the like.

  The communication interface 103 is a network interface card or the like. The HDD 104 stores programs, tables, and the like that operate the functions shown in FIGS.

  The CPU 101 reads a program that executes the same processing as each processing unit shown in FIGS. 3, 5, and 7 from the HDD 104 and develops it in the memory 102, which will be described with reference to FIGS. 3, 5, and 7. Run processes that perform each function.

  For example, this process performs the same function as each processing unit of the call control server 20. Specifically, the CPU 101 reads a program having the same function as each processing unit included in the software control device 21 and the U-Plane control device 25 from the HDD 103 or the like. Then, the CPU 101 executes a process for executing the same processing as the software control device 21 and the U-PLANE control device 25.

  As described above, the server 100 operates as an information processing apparatus that executes a communication method by reading and executing a program. The server 100 can also realize the same function as the above-described embodiment by reading the program from the recording medium by the medium reading device and executing the read program. Note that the program referred to in the other embodiments is not limited to being executed by the server 100. For example, the present invention can be similarly applied to a case where another computer or server executes the program or a case where these programs cooperate to execute the program.

DESCRIPTION OF SYMBOLS 10 Distribution server 11 Communication control part 12 Call distribution table 13 Usage rate monitoring part 14 Congestion detection part 15 Transfer instruction part 16 Notification receiving part 17 Signal transmission / reception part 18 Distribution control part 20, 40 Call control server 21, 41 Soft control Device 22, 42 Signal distribution control unit 23, 43 C-PLANE control unit 23a Station data table 23b Congestion detection unit 23c Station data transmission unit 23d, 43d Incoming signal control unit 23e, 43e Signal analysis unit 23f, 43f Session control unit 23g, 43g Service control unit 24, 44 U-PLANE control unit 24a, 44a Outgoing signal control unit 24b, 44b STM line control unit 24c, 44c ATM line control unit 25, 45 U-PLANE control unit 25a-1, 25a- n, 45a-1, 45a-n STM physical line 25b-1, 25b- n, 45b-1, 45b-n ATM physical line 43a Own station data table 43b Other station data table 43c Station data receiver

Claims (7)

In a communication system including a first call control server device and a second call control server device,
The first call control server device includes:
When detecting congestion, the first call control server device a station data list which associates the line information telephone number and the terminal device used by each terminal device as a target of the call control, the second A transmitter for transmitting to the call control server device;
The second call control server device
A first receiver for receiving the station data list from the first call control server device;
A second receiving unit for receiving a call control request to the terminal device transmitted to the first call control server device;
When the call control request is received by the second receiving unit, C-Plane control is executed on behalf of the first call control server device, and a destination related to the destination of the call control from the list of the station data A response unit for identifying information and responding to the first call control server device;
The first call control server device includes:
The second call control server device executes U-Plane control using the destination information that is the execution result of C-Plane control executed on behalf of the first call control server device, and the terminal device communication system, comprising a connecting portion for establishing a session. The communication system further includes a distribution server device to divide Ri vibration the call control request to the call control server device,
The distribution server device
A prediction unit for predicting a load transition from the load information of each call control server device;
An instruction to transmit the station data list to the second call control server device when the prediction unit predicts that the load of the first call control server device exceeds a threshold value within a predetermined time. The communication system according to claim 1, further comprising: an instruction transmission unit that transmits to the call control server device. The communication system includes a plurality of second call control server devices,
The distribution server device distributes the call control request to the terminal device at a ratio for smoothing each load based on the load transition of each second call control server device predicted by the prediction unit. The communication system according to claim 2, further comprising a distribution unit. When the distribution server device acquires load information of the first call control server device and detects that the congestion is released, the distribution server device detects the release of the congestion, and after the predetermined time has elapsed, A notification unit that notifies the call control server device of the release of the congestion,
The transmission unit of the first call control server device requests the second call control server device to delete the station data list when the notification of congestion release is received from the distribution server device. ,
Response portion of the second call control server, when receiving the deletion request of the station data list from said first call control server, to claim 2, characterized in that to remove the station data list The communication system described.   When the notification unit of the distribution server device detects that the congestion has been released, the notification unit of the first call control server device and the second caller at predetermined time intervals until the predetermined time elapses. The communication system according to claim 4, wherein a ratio of call control requests to the terminal device distributed to the call control server device is changed. Oite the communication method suitable for a communication system including a first call control server and the second call control server,
The first call control server device
When detecting congestion, the first call control server device a station data list which associates the line information telephone number and the terminal device used by each terminal device as a target of the call control, the second Sent to the call control server device,
The second call control server device is
Receiving the station data list from the first call control server device;
Receiving a call control request to the terminal device transmitted to the first call control server device;
When the call control request is received, C-Plane control is executed on behalf of the first call control server device, destination information relating to the destination of the call control is specified from the list of the station data, and the first In response to one call control server device,
The first call control server device
The terminal device performs U-Plane control using the destination information which is the execution result of C-Plane control executed by the second call control server device on behalf of the first call control server device, and the terminal device A communication method characterized by executing a process for establishing a session with the client . In the call control server device in a communication system including a call control server device and another call control server device,
When detecting congestion, the call control server device a station data list which associates the line information telephone number and the terminal device used by each terminal device as a target of the call control, the other call control server device A transmission unit for transmitting to
Using destination information relating to the destination of the call control identified from the list of the station data, which is the execution result of the C-Plane control executed by the other call control server device on behalf of the call control server device, U A call control server device comprising: a connection unit that executes Plane control to establish a session with the terminal device.

Images